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Acetylene-based frequency stabilization of a laser system for potassium laser cooling

Charbel Cherfan, Isam Manai, Samir Zemmouri, Jean Claude Garreau, Jean‐François Clément, Pascal Szriftgiser, Radu Chicireanu

Published Dec 17, 2019• 3 citations
OpenAlex

Abstract

We demonstrate a laser frequency stabilization technique for laser cooling of potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrational transitions of the acetylene molecule (12 C 2 H 2). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the 41 K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.

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Acetylene-based frequency stabilization of a laser system for potassium laser cooling.

Charbel Cherfan, Isam Manai, Samir Zemmouri +4 more

We demonstrate a laser frequency stabilization technique for laser cooling of potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrational transitions of the acetylene molecule (12C2H2). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the 41K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.

arXiv:1909.11631•Optics Express•Jan 2, 2020•13 citations

Multi-frequency telecom fibered laser system for potassium laser cooling

Charbel Cherfan, Maxime Denis, Denis Bacquet +7 more

We describe a compact and versatile multi-frequency laser system for laser-cooling potassium atoms by frequency doubling a fiber-optic telecom beam (≃1534 or 1540 nm). Low-power fiber-based telecom lasers and components generate a single beam containing the cooling and repumper half frequencies, subsequently amplified by a high-power amplifier. A final free-space second-harmonic generation stage provides a single beam with typically 2.5 W at quasi-resonant frequencies (≃767 or 770 nm) with high-quality mode and ready for laser cooling. This allowed us to trap up to 4×109 41K atoms with fast loading times (2.5 s) at sub-Doppler temperatures of 16 μK. This opens promising perspectives toward versatile and transportable ultracold atom setups.

arXiv:2109.03864•Applied Physics Letters•Nov 15, 2021•3 citations

Laser Frequency Stabilization for Narrow Linewidth Cooling of Lithium-6

Adam Reed

Laser cooling to micro-Kelvin temperatures requires a laser with active frequency stabilization. The linewidth of an atomic transition sets a lower bound on the Doppler cooling temperature. The 2s-2p transition in lithium-6 has a Doppler temperature of ~140 μK In contrast, the 2s-3p transition has a narrower linewidth and thus provides a lower temperature limit of ~20 μK. We present a method for stabilizing a laser to an atomic line in a vapor cell using modulation transfer spectroscopy and a home-built lock-in amplifier. Our results demonstrate successful locking of a 323 nm laser to the 2s-3p transition. The stabilized laser provides a second stage of magneto-optical trapping that results in a factor of ∼5 increase in the phase space density before evaporating to degeneracy in an optical dipole trap.

•Mar 1, 2011•0 citations

A Laser System for Gray-Molasses Cooling on the D1 Transition of an Atomic Gas of 39K

Baraa Shammout

In this work we present the design and the construction of a laser system for cooling an atomic gas of potassium 39K on the D1-Line by gray molasses technique. The seed laser is an Interference-filter-stabilized external-cavity diode laser (ECDL). The laser frequency is stabilized to one of the atomic features of 39K D1-transition thanks to frequency modulation (FM) spectroscopy. The low seed power is then amplified by means of tapered amplifier (TA). Finally, the cooling and repumping beams are generated and blue-detuned from the atomic transitions |F = 2> → |F'= 2> and |F = 1> → |F'= 2> using two acousto-optic modulators (AOMs).

•Jan 1, 2020•2 citations

Blue laser for precision spectroscopy: toward optical frequency standard referenced to laser cooled calcium atoms

Vera Grishina

Optical frequency standards with the reference to a narrow electronic transition of a laser-cooled collection of neutral atomic particles are becoming essential tools of research in modern precision physics experiments. In the core of a building block of an optical frequency standard is the optical continuous wave laser that has a good spectral purity of the emitted light. Such a stable optical oscillator is highly desirable in high resolution spectroscopy, if it emits in a good quality beam at a short visible wavelength. This Master thesis explores efficient techniques for building such an optical frequency source intended for use in the cooling and trapping of Calcium atoms scheme. The strong dipole transition at the blue wavelength in the atomic Calcium is needed to reduce the kinetic energy of atoms by nearly six orders of magnitude. A further reduction in the thermal energy of the laser cooled atoms is required to locate with ultra-high precision the 400 Hz narrow clock transition of the stable 40Ca isotope. The experimental methods that achieve this and approach sub-microkelvin temperature of the laser cooled bosonic isotopes of alkaline earths are inspected. The blue laser with a uniform intensity distribution in the beam is useful to maintain the trapped number of cold atoms during these experiments. The spectroscopic properties of the relative transitions in Calcium atom are also reviewed following relevant publications in the area. The constructed blue laser can be used as a primary wavelength source in the lasers network for cooling and trapping of Calcium atoms. These experiments will constitute part of the project to build an optical atom clock referenced to 40Ca narrow linewidth transition. The blue laser is constructed by generating second harmonic in a Potassium Niobate crystal, which is temperature controlled to use a type-I noncritical phase-matching of the optical nonlinear process. The power of the intracavity-generated second harmonic depends on the resonance properties of the optical resonator where this nonlinear crystal is placed. The study is aimed at characterising the designed optical resonator and the experimental parameters that describe it. The formula is derived that relates the resonance power enhancement coefficient with finesse and the power coupling contrast of a passive optical cavity. The obtained relationship is verfied during the experiments. The produced efficiency of the intracavity second harmonic generation is approx. 0.0023 mWblue/(mWred)2. The research work also examines the noise characteristics of the infrared diode laser that is used as a pump source for the intracavity generated second harmonic and determines the spectroscopic precision of the produced blue light. The frequency locking experiment is analysed using the unbalanced scheme of the polarisation stabilisation technique. The designed optical buildup cavity became a part of the unbalanced frequency discriminator in such a scheme. The results demonstrate high gain of frequency noise suppression of the stabilised laser. The unbalanced arrangement of the H}ansch-Couillaud technique has been possible due to a very low amplitude noise of semiconductor lasers.

•Jan 1, 2008•0 citations

Laser frequency stabilization by bichromatic saturation absorption spectroscopy

Genko T. Genov, Tim Lellinger, Thomas Halfmann +1 more

We present and analyze a bichromatic version of the well-known saturation absorption spectroscopy technique used to stabilize lasers to atomic resonances without Doppler broadening. We show that the spectroscopic properties can be transferred between two transitions at very different wavelengths by spectral hole burning in a Doppler-broadened atomic ensemble. Specifically, we demonstrate that this technique can be used to stabilize a laser to the D1 line of Rb87 by obtaining a saturation absorption spectrum with a strong pump laser stabilized to the D2 line. This allows for more freedom in the choice of the probe laser frequency offsets compared to conventional saturation absorption spectroscopy. We compare our experimental results to an analytical model and numerical results based on rate equations.

Journal of the Optical Society of America B•Aug 31, 2017•17 citations
We demonstrate a laser frequency stabilization technique for laser cooling of potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrational transitions of the acetylene molecule (12 C 2 H 2). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the 41 K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.
We demonstrate a laser frequency stabilization technique for laser cooling of potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrational transitions of the acetylene molecule (12C2H2). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the 41K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.
We describe a compact and versatile multi-frequency laser system for laser-cooling potassium atoms by frequency doubling a fiber-optic telecom beam (≃1534 or 1540 nm). Low-power fiber-based telecom lasers and components generate a single beam containing the cooling and repumper half frequencies, subsequently amplified by a high-power amplifier. A final free-space second-harmonic generation stage provides a single beam with typically 2.5 W at quasi-resonant frequencies (≃767 or 770 nm) with high-quality mode and ready for laser cooling. This allowed us to trap up to 4×109 41K atoms with fast loading times (2.5 s) at sub-Doppler temperatures of 16 μK. This opens promising perspectives toward versatile and transportable ultracold atom setups.
Laser cooling to micro-Kelvin temperatures requires a laser with active frequency stabilization. The linewidth of an atomic transition sets a lower bound on the Doppler cooling temperature. The 2s-2p transition in lithium-6 has a Doppler temperature of ~140 μK In contrast, the 2s-3p transition has a narrower linewidth and thus provides a lower temperature limit of ~20 μK. We present a method for stabilizing a laser to an atomic line in a vapor cell using modulation transfer spectroscopy and a home-built lock-in amplifier. Our results demonstrate successful locking of a 323 nm laser to the 2s-3p transition. The stabilized laser provides a second stage of magneto-optical trapping that results in a factor of ∼5 increase in the phase space density before evaporating to degeneracy in an optical dipole trap.
In this work we present the design and the construction of a laser system for cooling an atomic gas of potassium 39K on the D1-Line by gray molasses technique. The seed laser is an Interference-filter-stabilized external-cavity diode laser (ECDL). The laser frequency is stabilized to one of the atomic features of 39K D1-transition thanks to frequency modulation (FM) spectroscopy. The low seed power is then amplified by means of tapered amplifier (TA). Finally, the cooling and repumping beams are generated and blue-detuned from the atomic transitions |F = 2> → |F'= 2> and |F = 1> → |F'= 2> using two acousto-optic modulators (AOMs).
Optical frequency standards with the reference to a narrow electronic transition of a laser-cooled collection of neutral atomic particles are becoming essential tools of research in modern precision physics experiments. In the core of a building block of an optical frequency standard is the optical continuous wave laser that has a good spectral purity of the emitted light. Such a stable optical oscillator is highly desirable in high resolution spectroscopy, if it emits in a good quality beam at a short visible wavelength. This Master thesis explores efficient techniques for building such an optical frequency source intended for use in the cooling and trapping of Calcium atoms scheme. The strong dipole transition at the blue wavelength in the atomic Calcium is needed to reduce the kinetic energy of atoms by nearly six orders of magnitude. A further reduction in the thermal energy of the laser cooled atoms is required to locate with ultra-high precision the 400 Hz narrow clock transition of the stable 40Ca isotope. The experimental methods that achieve this and approach sub-microkelvin temperature of the laser cooled bosonic isotopes of alkaline earths are inspected. The blue laser with a uniform intensity distribution in the beam is useful to maintain the trapped number of cold atoms during these experiments. The spectroscopic properties of the relative transitions in Calcium atom are also reviewed following relevant publications in the area. The constructed blue laser can be used as a primary wavelength source in the lasers network for cooling and trapping of Calcium atoms. These experiments will constitute part of the project to build an optical atom clock referenced to 40Ca narrow linewidth transition. The blue laser is constructed by generating second harmonic in a Potassium Niobate crystal, which is temperature controlled to use a type-I noncritical phase-matching of the optical nonlinear process. The power of the intracavity-generated second harmonic depends on the resonance properties of the optical resonator where this nonlinear crystal is placed. The study is aimed at characterising the designed optical resonator and the experimental parameters that describe it. The formula is derived that relates the resonance power enhancement coefficient with finesse and the power coupling contrast of a passive optical cavity. The obtained relationship is verfied during the experiments. The produced efficiency of the intracavity second harmonic generation is approx. 0.0023 mWblue/(mWred)2. The research work also examines the noise characteristics of the infrared diode laser that is used as a pump source for the intracavity generated second harmonic and determines the spectroscopic precision of the produced blue light. The frequency locking experiment is analysed using the unbalanced scheme of the polarisation stabilisation technique. The designed optical buildup cavity became a part of the unbalanced frequency discriminator in such a scheme. The results demonstrate high gain of frequency noise suppression of the stabilised laser. The unbalanced arrangement of the H}ansch-Couillaud technique has been possible due to a very low amplitude noise of semiconductor lasers.
We present and analyze a bichromatic version of the well-known saturation absorption spectroscopy technique used to stabilize lasers to atomic resonances without Doppler broadening. We show that the spectroscopic properties can be transferred between two transitions at very different wavelengths by spectral hole burning in a Doppler-broadened atomic ensemble. Specifically, we demonstrate that this technique can be used to stabilize a laser to the D1 line of Rb87 by obtaining a saturation absorption spectrum with a strong pump laser stabilized to the D2 line. This allows for more freedom in the choice of the probe laser frequency offsets compared to conventional saturation absorption spectroscopy. We compare our experimental results to an analytical model and numerical results based on rate equations.